[cfe-dev] libclang , clang_Cursor_isAnonymous what is an anonymous declaration

[Nikola Smiljanic via cfe-dev]

My guess would be that language options aren't set correctly. Comment
in BuildAnonymousStructOrUnion (that calls setAnonymousStructOrUnion)
says:

Anonymous unions are a C++ feature (C++ [class.union]) and a C11
feature; anonymous structures are a C11 feature and GNU C++ extension.


On Fri, Nov 13, 2015 at 4:52 AM, cedlemo via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
>
> When I use clang in order to parse the same file, I 'm not able to find anonymous struct or union decl:
> even if I use the anonymous examples of the documentation.
>
>
> class MyASTConsumer : public clang::ASTConsumer
> {
>  public:
>  MyASTConsumer() : clang::ASTConsumer() { }
>  virtual ~MyASTConsumer() { }
>  virtual void HandleTagDeclDefinition( clang::TagDecl * d)
>  {
>    if (d->isStruct())
>      std::cout << "struct" << std::endl;
>    if (d->isUnion())
>      std::cout << "union" << std::endl;
>    clang::RecordDecl *r; r = llvm::cast(d);
>    if( r->isAnonymousStructOrUnion() )
>    {
>      std::cout << "RecordDecl Anonymous : " << std::endl;
>    }
>    }
>  };
>
> int main()
> {
>   using clang::CompilerInstance;
>   using clang::TargetOptions;
>   using clang::TargetInfo;
>   using clang::FileEntry;
>   using clang::Token;
>   using clang::ASTContext;
>   using clang::ASTConsumer;
>   using clang::Parser;
>   using clang::DiagnosticOptions;
>   using clang::TextDiagnosticPrinter;
>   CompilerInstance ci;
>   DiagnosticOptions diagnosticOptions;
>   ci.createDiagnostics();
>   std::shared_ptr pto = std::make_shared();
>   pto->Triple = llvm::sys::getDefaultTargetTriple();
>   TargetInfo *pti = TargetInfo::CreateTargetInfo(ci.getDiagnostics(), pto);
>   ci.setTarget(pti);
>   ci.createFileManager();
>   ci.createSourceManager(ci.getFileManager());
>   ci.createPreprocessor(clang::TU_Complete);
>   ci.getPreprocessorOpts().UsePredefines = false;
>   MyASTConsumer *astConsumer = new MyASTConsumer();
>   ci.setASTConsumer(llvm::make_unique(*astConsumer));
>   ci.createASTContext();
>   const FileEntry *pFile = ci.getFileManager().getFile("record_decls.c");
>   clang::FileID id = ci.getSourceManager().createFileID(pFile, clang::SourceLocation(), clang::SrcMgr::C_User);
>   ci.getSourceManager().setMainFileID(id);
>   ci.getDiagnosticClient().BeginSourceFile(ci.getLangOpts(), &ci.getPreprocessor());
>   clang::ParseAST(ci.getPreprocessor(), astConsumer, ci.getASTContext());
>   ci.getDiagnosticClient().EndSourceFile();
>   return 0;
>
>  }
>
>
> On 07/11/2015 14:18, cedlemo via cfe-dev wrote:
>
> I have some difficulties to understand what are anonymous structures declaration (or union) .
>
> From this link: http://clang.llvm.org/doxygen/classclang_1_1RecordDecl.html#ad2dd151523eecb8d15149cc0937c3dff
>
> this is an anonymous declaration
>
> union { int i; float f; };
>
> and not this
>
> union X { int i; float f; };
> union { int i; float f; } obj;
>
>
> But if I make some tests:
>
>
>
> #include <stdio.h>
> #include "clang-c/Index.h"
> /*
> compile with:
> clang -lclang -o anonymous_record_decl_check anonymous_record_decl_check.c
> */
> static enum CXChildVisitResult
> visitor(CXCursor cursor, CXCursor parent, CXClientData data)
> {
>   CXSourceLocation loc;
>   CXFile file;
>   unsigned line;
>   unsigned column;
>   unsigned offset;
>   if (clang_getCursorKind(cursor) == CXCursor_StructDecl)
>   {
>     printf("sentinel %d\n", __LINE__);
>     loc = clang_getCursorLocation(cursor);
>     clang_getSpellingLocation(loc,
>                               &file,
>                               &line,
>                               &column,
>                               &offset);
>
>     printf("sentinel %d\n", __LINE__);
>     printf("line: %d anon ? %d\n", line, clang_Cursor_isAnonymous(cursor));
>   }
>
>   if (clang_getCursorKind(cursor) == CXCursor_UnionDecl)
>   {
>     printf("sentinel %d\n", __LINE__);
>     loc = clang_getCursorLocation(cursor);
>     printf("sentinel %d\n", __LINE__);
>     clang_getSpellingLocation(loc,
>                               &file,
>                               &line,
>                               &column,
>                               &offset);
>     printf("line: %d anon ? %d\n", line, clang_Cursor_isAnonymous(cursor));
>   }
>   return CXChildVisit_Recurse; // visit complete AST recursivly
> }
>
> int main(int argc, char *argv[]) {
>   CXIndex Index = clang_createIndex(0, 1);
>   CXTranslationUnit TU = clang_createTranslationUnitFromSourceFile(Index,
> "record_decls.c",
>                                                       0,
>                                                       0,
>                                                       0,
>                                                       0);
>
>   clang_visitChildren(clang_getTranslationUnitCursor(TU), visitor, 0);
>
>   clang_disposeTranslationUnit(TU);
>   clang_disposeIndex(Index);
>   return 0;
> }
>
>
> with the file that is parsed ( record_decls.c ):
>
> struct { int a; char b; };
> struct tata { int c; double e;};
> union { int i; float f; };
> union X { int i; float f; };
>
>
>
> I have this output:
>
> sentinel 17
> sentinel 25
> line: 1 anon ? 0
> sentinel 17
> sentinel 25
> line: 2 anon ? 0
> sentinel 31
> sentinel 33
> line: 3 anon ? 0
> sentinel 31
> sentinel 33
> line: 4 anon ? 0
>
>
> Which means that all my declarations return the same value form clang_Cursor_isAnonymous
>
> Which means, well I don't really know, here is the comments from the headers:
>
> /**
>  * \brief Determine whether the given cursor represents an anonymous record
>  * declaration.
>  */
>
> Any ideas?
>
>
> cedlemo
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